Test impact of macro typography settings on readability

## Variants

1. **Control 1**: the current settings.
2. **Control 2 - No spacing**: consecutive paragraphs have no spacing between them.
3. **Variant 1 - No spacing, indents**: consecutive paragraphs have no spacing between them. A paragraph that follows another will have an indent.
4. **Variant 2 - More spacing**: line height and spacing between paragraphs are higher than the control.

It is set to run on 10% of our readers.

## Hypothesis

Macro typography settings have an impact on readability, thus impacting content consumption of our readers.

## Predictions

- Control 2 (no spacing between paragraphs) induces reading fatigue, leading to less content consumption
- Variant 1 (no spacing, indents)  is as readable as control 1, and better for mobile especially thanks to HiDPI displays
- Variant 2 (more spacing) creates a disjointed reading experience for mobile users (more scrolling required)

We expect variant 1 and control 1 to be on par, which should leave us with an easier choice between the two.

AB testing does not tell the whole story, and this should lead to another test: how do people *feel* about those settings.

## Data

- Scroll % across the article page
- Time spent on article page
- Bounce rate

And we can probably refine this measures depending on what bucket people are in (one-time users vs loyal returning users).

![Oops](http://i.imgur.com/uP2Urzr.gif)